oslo.concurrency/releasenotes/notes/add-option-for-fair-locks-b6d660e97683cec6.yaml
Chris Friesen 2b55da68ae Add support for fair locks
This adds support for a "fair" variant of the lock.  When there are
multiple entities within a single process that are blocked waiting
for the lock the fair lock will ensure that they acquire the lock
in FIFO order.

For now at least, when fair locks are in use we don't support
the "semaphores" argument.

If external locks are enabled, the inter-process ordering will be
determined by the underlying OS lock ordering and process scheduling.

Change-Id: I37577becff4978bf643c65fa9bc2d78d342ea35a
2018-11-02 10:40:23 -06:00

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YAML

---
prelude: >
This release includes optional support for fair locks. When fair locks
are specified, blocking waiters will acquire the lock in the order that
they blocked.
features:
- |
We now have optional support for ``fair`` locks. When fair locks are
specified, blocking waiters will acquire the lock in the order that they
blocked. This can be useful to ensure that existing blocked waiters do
not wait indefinitely in the face of large numbers of new attempts to
acquire the lock. When specifying locks as both ``external`` and ``fair``,
the ordering *within* a given process will be fair, but the ordering
*between* processes will be determined by the behaviour of the underlying
OS.